1. Field of the Invention
The present invention relates to an image communication apparatus and method therefor, and more particularly to a moving image transmission apparatus adapted for use in a television-telephone apparatus or a television conference system.
2. Related Background Art
In such a moving image communication system, it is preferable to be able to transmit as many images as possible per second, while maintaining satisfactory image quality in each image frame. In the conventional moving image encoding method, since the available amount of codes is by far smaller than the entropy of the image, it has been customary to maintain the image quality in a state of semi-moving image in which the number of image frames per second is limited, or to maintain a sufficient number of image frames per second for the moving image, while sacrificing the image quality. Stated differently, in the conventional method, the image quality and the number of image frames per second are in a trade-off relationship.
Also in the television-telephone or the like, there is proposed a configuration of automatically detecting a part of the object, for example the face of a person, and preferentially allotting codes to the part, thereby enabling transmission of a sufficient number of image frames per second for a moving image, while securing the image quality in a part of the image frame.
However, in such a conventional method of preferentially assigning codes to the face portion of the object, there may eventually result in an error in the automatic detection of the face portion, and such a face portion may not necessarily be the most important part in the image frame. For example, the transmitting person or the receiving person may wish to observe the background or an article held by the person, rather than the person himself, and the above-mentioned conventional method is unable to meet such complex and varying requirements.